High bulk density extruded propellant for small arms cartridges

ABSTRACT

Extruded single or double base propellants for cartridges up to and including 7.62 mm, the propellant having improved bulk densities which are achieved by providing a non-fibrous matrix and smooth surfaces to the individual small arms propellant grains.

United States Patent 1191 Stiefel et al. 1 Aug. 5, 1975 15 1 HIGH BULK DENSITY EXTRUDED 2329.575 9/1943 A111s6n et a1 149/10 PROPELLANT FOR SMALL ARMS 2.346.125 4/1944 Goodyear 149/10 1865,72) 12/1958 Foster et a1... 149/10 X CARTRIDGES 3.163.567 12/1964 Silk 102/104 x [75] Inventors: Ludwig Stiet'el; Marvin E. Levy, 3,223.756 12/1965 Goodyear et a1 264/3 8 both f phi|ade]phiu p Mani 3.704,]85 11/1972 Cooner 149/10 X silversein, westmont Nil 3.706.278 12/1972 Stiefel Cl 31 102/104 [73] Assignee: The United States of America as represented b th Secretary f th Primary E.raminer-Benjamin R. Padgett Army, Washington, DC. Assistant Etaminer-E. A. Miller I Attorney, Agent, or FirmNathan Edelberg; Robert P. [22] Filed. Mar. 19, 1973 Gibson; Kalman Pollen [211 App11 N0.: 342,927

52 us. (:1. 102/104; 149/2; 149/10; 1 1 ABSTRACT 149/198; 149/98; 149/100; 264/3 B; 264/3 C [511 11.1.0. F428 5/16; C068 25/26 i Smg'e base Pwpellams [58] Field of Search 102/104,. 149/2 10 198' trldges up to and Including 7.62 mm, the propellant 149/98 264,3 B 3 C having improved bulk densities which are achieved by 1 providing a non-fibrous matrix and smooth surfaces to [56] References cued the individual small arms prope1lant grains.

UNITED STATES PATENTS '2 Claims No Drawings 2.179.315 11/1939 Allison 149/10 HIGH BULK DENSITY EXTRUDED PROPELLANT FOR SMALL ARMS CARTRIDGES This invention described herein may be manufactured, used, and licensed by or for the Government for herein presented for illustrative purposes, all percentages being by weight:

EXAMPLE I Sin le base, solid c linder: governmental purposes without the payment to us of 5 g y any royalty thereon.

This invention relates to propellants and more partic- Nitrocellulose 94% (13 ;5%N) ularly concerns higher bulk density extruded propel- Ethyl n Dirncihaci'ylale 4 Diphcnylamine l lants for small arms cartridges. Potassium Sulfate 1 The bulk density of ball propellants for small arms Graphite Coating .2% (added) cartridges remains relatively constant from 20 to 7.62 T

mm. As shown in Table l below, the same does not geni 1 5 erally hold true for extruded propellants: Bulk Density .9l5 gm/cc TABLE I Comparison of Bulk Density of Extruded and Ball Propeilants Single Base Ball Propcllant Extruded Propellant Type Bulk Density Type Bulk Density gm/cc gm/cc mm T130 (Mark xii) [MR 6962 0970 WG 880 0.960 20mm M90 Series IMR 7013 0.950 WC 875 0.960 20mm M50 Series IMR7005 0.955 WC 876 0.960 Caliber .50 IMR 50i0 0.950 WC 860 0.950 Caliber IMR 4895 0.900 WC 852 0.940 7.62 mm iMR 8138M 0885 WC 846 0.980 5.56mm IMR 8208M 0890 WC 8 44 0.980

The considerably lower bulk density of the extruded EXAMPLE ll propellants in the 5.56 and 7.62 mm caliber range Double base 50nd cylinder. when compared to the ball propellant has been the 30 cause of several problems in their efficient utilization in small arms ammunition. For example, (a) excessively low cyclic rates have at times resulted, when used f? in the Ml6 rifle, thereby causing increased malfunc- Ethylene Dirnethacrylate 4 tions, (b) ballistic requirements frequently could not be P l Graphite Coating .2% (added) satisfied because of insufficient propellant, and so on. m) 1 With the trend toward modern, compact, high velocity Length 12 Diameter .025" cartridges, optimum propellant loading densities for Bulk Density 920 small arms cartridges must be made available to our military forces. 40

Accordingly, it is a principal object of this invention to provide extruded propellants for the smaller caliber cartridges with improved bulk densities. EXAMPLE In Other objects and features of the invention will be- Single base, mono'perforatedl come apparent as the invention is more fully hereinaf- Same P IiOH and L/D as in Example I. ter disclosed.

Briefly, we have discovered that improvements in bulk density of single or double base extruded propellants can be obtained through the use of conventional Length .031" equipment by altering the matrix and surfaces of the g p Cl ora IOII individual propellant grains. I Bulk Dem), 910 gm/cc More specifically, an increase in bulk density will be obtained when using propellant grains having a cylindrical shape wherein its diameter and length are substantially the same, but more importantly, by imparting substantially non-fibrous characteristics to these ex- EXAMPLE W truded propellant grains.

A relationship exists between bulk density and length Double base wono'perforatedj E 1 to diameter ratio (L/D) of the propellant grain, i.e., for Same Composmon and LID as m P e a given grain length, the bulk density will increase as L/D is made to approximate 0.9 to l.l. The grains may be extruded solid cylinders, or mono-perforated For single base, solid cylinder, the grain length will nor- Length mally not exceed about 0.025 inch, whereas about f Perforation .007 0.027 inch will define the maximum length of double Bulk Density 9 base solid cylinders.

In order to more clearly define one aspect of our invention, namely, the effect of L/D upon bulk density, the following examples for fibrous propellants are Referring to Table l, and more particularly to IMR 8138M, which is a single base extruded propellant having the identical composition as shown in Example I above but with the following geometry:

IMR 8138M L/D L4 Length .042" Diameter .030" Perforation .007 Bulk Density .885 gm/cc As shown in Examples III (perforated) and I (unperforated), the bulk densities will be increased from 0.885 to 0.910 and 0.915 gm/cc respectively by the expediency of providing an L/D of l. Ballistic data are not supplied for our higher density propellants since it is well understood in the art that higher bulk densities will provide greater charges with a concomitant increase in projectile velocity. In other propellant batches, illustrated by Examples I through IV, the bulk densities did not vary more than 0.002 gm/cc when MD was varied from 0.9 to l.l.

Conventional solvent extruded propellants have a relatively rough surface because, in the manufacturing process, the nitrocellulose retains much of its fibrous character. Upon extrusion, these fibers orient themselves in the direction of the extruding force. When the solvent-wet grains dry, the surface becomes rough because of the oriented fibrous structure. We have discoverd that a major improvement in bulk density will result when the surfaces of the propellant grains are rendered smooth and non-fibrous. This desired object may readily be achieved through the use of colloided nitrocellulose as a starting material, or the grains may be smoothed by tumble-polishing in a suitable mill, for example, or the like.

Examples of these improved bulk density extruded propellants are presented below:

EXAMPLE V Single base, solid cylinder, smooth surfaced: Same composition and dimensions as in Example I, but colloided nitrocellulose used as a starting material.

Bulk Density .938 gm/cc EXAMPLE VI Double base, solid cylinder, smooth surfaced: Same composition and dimensions as in Example II, but colloided nitrocellulose used as a starting material.

Bulk Density .947 gm/cc EXAMPLE VII Single base, mono-perforated, smooth surfaced: Same composition, and dimensions as in Example III, but colloided nitrocellulose used as a starting material.

Bulk Density .932 gm/cc EXAMPLE VIII Double base, mono-perforated, smooth surfaced: Same composition, and dimensions as in Example IV, but colloided nitrocellulose used as a starting material.

Bulk Density .940 gm/cc Thus, it is seen for similar compositions and dimensions, the use of colloided nitrocellulose provided an average increase of 0.024 gm/cc in bulk density.

In other propellant batches illustrated by Examples V through VIII, bulk density did not vary more than .002 gm/cc when L/D was varied from 0.9 to L].

In fabricating our improved propellants, conventional equipment will be used. The water wet nitrocellulose is first dehydrated by alcohol displacement in a dehydrating press. The alcohol wet nitrocellulose may now be fed into a suitable mixer and then stabilizers, plasticizers and other additives (as required), and solvents such as alcohol and acetone will be added. It is interesting to note here that a modest improvement in bulk density results if the acetone to alcohol ratio is increased to approximately 3 to l, over their conven tional l to 1 ratio. Similarly, if the solvent to solids ratio is increased to 7 to 3 in lieu of the standard I to 2, which promotes increased colloidization of the matrix, a small increase in bulk density will again be realized. These increased ratios will necessitate a drying down of the mix at the end of the mixing cycle in order that a dough of proper consistency will be achieved. Another slight improvement in density results when these mixed ingredients are permitted to age for a period of at least 24 hours prior to extrusion.

The mix will then be subjected to maceration which assists in shredding the fibrous mix. The dough will then be consolidated in a blocking press and extruded through a macaroni or screening press, which further destroys the fibrous structure of the nitrocellulose. Prior to final extrusion, the dough will again be blocked in a blocking press. The extruded strands are then fed into a cutter for cutting into desired lengths. The cut propellant will then be subjected to standard solvent removal processes which may include forced air drying at elevated temperatures and water dry processes which will lower the amount of total volatiles remaining in the finished propellant.

In general, any operation which smoothes the surfaces of the grain by grinding off sharp edges thereof will improve bulk density of the grains. Grinding may be accomplished while the propellant is in the undried or green" state. The propellant may be finished" by coating with deterrent using standard methods and by coating with small amounts of graphite.

We wish it to be understood that we do not desire to be limited to the exact details described, for obvious modifications will occur to a person skilled in the art.

We claim:

1. An extruded propellant for small arms cartridges of 0.30 caliber and smaller ammunition, said propellant having a minimum bulk density of 0.932 gm/cc and comprising cylindrical grains having a length to outer diameter ratio of approximately 0.9 to 1.1, and wherein said propellant grains comprise at least 85% colloided nitrocellulose, by weight, said colloided propellant grains being substantially non-fibrous.

2. The extruded propellant of claim 1 wherein said propellant grains are unperforated single base.

3. The extruded propellant of claim 1 wherein said propellant grains are unperforated double base.

4. The extruded propellant of claim 1 wherein said propellant grains are mono perforated single base.

5. The extruded propellant of claim 1 wherein said propellant grains are mono-perforated double base.

6. The extruded propellant of claim 1 wherein said propellant grains comprise by weight:

94% Colloided Nitrocellulose (13.15%N) 4% Ethylene dimethacrylate 1% Diphenylamine l% Potassium Sulfate 0.2% (added) Graphite Coating 7. The extruded propellant of claim 1 wherein said propellant grains comprise by weight:

85% Colloided Nitrocellulose (13.15%N) Nitroglycerine 4% Ethylene dimethacrylate 1% Diphenylamine 0.2% (added) Graphite Coating 8. The extruded propellant of claim 6 wherein said propellant grains are unperforated single base having a length of 0.025 inch and diameter of 0.025 inch and a bulk density of 0.938 gm/cc.

9. The extruded propellant of claim 7 wherein said propellant grains are unperforated double base having a length of 0.025 inch and diameter of 0.025 inch and a bulk density of 0.947 gm/cc.

10. The extruded propellant of claim 6 wherein said propellant grains are mono-perforated single base having a length of 0.031 inch, diameter of 0.03] inch, perforation of 0.007 inch, and a bulk density of 0.932 gm/cc.

11. The extruded propellant of claim 7 wherein said propellant grains are mono-perforated double base having a length of 0.035 inch, diameter of 0.035 inch, perforation of 0.007 inch, and a bulk density of 0.940 gm/cc.

12. An extruded propellant for small arms cartridges of 0.30 caliber and smaller ammunition, said propellant having a minimum bulk density of 0.932 gm/cc and comprising cylindrical grains having a length to outer diameter ratio of approximately 0.9 to 1.1, and wherein said propellant grains comprise at least colloided nitrocellulose by weight, said colloided propellant grains being substantially non-fibrous, colloidization of nitrocellulose achieved by dehydrating a water-wet nitrocellulose by alcohol displacement in a dehydrating press,

feeding said dehydrated nitrocellulose with alcohol and acetone into a mixer to form a mix, ratio of said acetone to said alcohol being approximately 3 to 1, ratio in said mix of total solvent to solids being 7 to 3,

subjecting said mix to a mixing cycle,

drying resultant mix to form a dough,

aging said dough at least 24 hours,

macerating said aged dough,

consolidating said macerated dough in a blocking press, and

extruding said consolidated dough through a macaroni or screening press. 

1. AN EXTRUDED PROPELLANT FOR SMALL ARMS CARTRIDGES OF 0.30 CALIBER AND SMALLER AMMUNITION, SAID PROPELLANT HAVING A MINIMUM BULK DENSITY OF 0.932 GM/CC AND COMPRISING CYLINDRICAL GRAINS HAVING A LENGTH TO OUTER DIAMETER RATIO OF APPROXIMATELY 0.9 TO 1.1, AND WHEREIN SAID PROPELLANT GRAINS COMPRISES AT LEAST 85% COLLIDED NITROCELLULOSE, BY WEIGHT, SAID COLLOIDED PROPELLANT GRAINS BEING SUBSTANTIALLY NON-FIBROUS.
 2. The extruded propellant of claim 1 wherein said propellant grains are unperforated single bAse.
 3. The extruded propellant of claim 1 wherein said propellant grains are unperforated double base.
 4. The extruded propellant of claim 1 wherein said propellant grains are mono-perforated single base.
 5. The extruded propellant of claim 1 wherein said propellant grains are mono-perforated double base.
 6. The extruded propellant of claim 1 wherein said propellant grains comprise by weight: 94% Colloided Nitrocellulose (13.15%N) 4% Ethylene dimethacrylate 1% Diphenylamine 1% Potassium Sulfate 0.2% (added) Graphite Coating
 7. The extruded propellant of claim 1 wherein said propellant grains comprise by weight: 85% Colloided Nitrocellulose (13.15%N) 10% Nitroglycerine 4% Ethylene dimethacrylate 1% Diphenylamine 0.2% (added) Graphite Coating
 8. The extruded propellant of claim 6 wherein said propellant grains are unperforated single base having a length of 0.025 inch and diameter of 0.025 inch and a bulk density of 0.938 gm/cc.
 9. The extruded propellant of claim 7 wherein said propellant grains are unperforated double base having a length of 0.025 inch and diameter of 0.025 inch and a bulk density of 0.947 gm/cc.
 10. The extruded propellant of claim 6 wherein said propellant grains are mono-perforated single base having a length of 0.031 inch, diameter of 0.031 inch, perforation of 0.007 inch, and a bulk density of 0.932 gm/cc.
 11. The extruded propellant of claim 7 wherein said propellant grains are mono-perforated double base having a length of 0.035 inch, diameter of 0.035 inch, perforation of 0.007 inch, and a bulk density of 0.940 gm/cc.
 12. An extruded propellant for small arms cartridges of 0.30 caliber and smaller ammunition, said propellant having a minimum bulk density of 0.932 gm/cc and comprising cylindrical grains having a length to outer diameter ratio of approximately 0.9 to 1.1, and wherein said propellant grains comprise at least 85% colloided nitrocellulose by weight, said colloided propellant grains being substantially non-fibrous, colloidization of nitrocellulose achieved by dehydrating a water-wet nitrocellulose by alcohol displacement in a dehydrating press, feeding said dehydrated nitrocellulose with alcohol and acetone into a mixer to form a mix, ratio of said acetone to said alcohol being approximately 3 to 1, ratio in said mix of total solvent to solids being 7 to 3, subjecting said mix to a mixing cycle, drying resultant mix to form a dough, aging said dough at least 24 hours, macerating said aged dough, consolidating said macerated dough in a blocking press, and extruding said consolidated dough through a macaroni or screening press. 